The present invention relates to saltwater cement compositions and, more particularly, to the use of a combination of latex stabilizers to prevent latex inversion in saltwater cement compositions and associated methods of cementing.
Cement compositions are commonly utilized in subterranean operations, particularly subterranean well construction and remedial operations. For example, in subterranean well construction, a pipe string (such as casing and liners) may be run into the well and cemented in place. The process of cementing the pipe string in place is commonly referred to as “primary cementing.” In a typical primary cementing operation, a cement composition may be pumped into an annulus between the walls of a well bore and the exterior surface of the pipe string disposed therein. The cement composition sets in the annular space, thereby forming an annular sheath of hardened, substantially impermeable cement that supports and positions the pipe string in the well bore and bonds the exterior surface of the pipe string to the walls of the well bore. Among other things, the annular sheath of set cement surrounding the pipe string functions to prevent the migration of fluids in the annulus, as well as protecting the pipe string from corrosion. Cement compositions also may be used in remedial cementing operations, such as squeeze cementing and the placement of cement plugs.
Heretofore, latex has been included in cement compositions for use in subterranean formations to improve various properties of the compositions. For example, latex may be included in a cement composition for fluid loss control, to provide resiliency to the set cement, and/or to reduce the issues associated with gas channeling. In general, latex used in cement compositions is often provided as a water-in-oil emulsion containing high quantities of natural or synthetic rubber (such as styrene-butadiene rubber). These cement compositions that include latex may be prepared using either freshwater of saltwater. By way of example, when cementing in an offshore well, seawater may be used to prepare the cement composition, thereby alleviating the necessity to transport freshwater to the offshore well location. Additionally, during a subterranean cementing operation, one or more salt containing zones may be encountered. Accordingly, to alleviate potential issues associated with the cement composition dissolving salt contained in these zones, saltwater may be used to prepare the cement compositions.
However, when latex is included in saltwater cement compositions, the latex will typically invert upon combination with the saltwater resulting in precipitation of the rubber whether in the form of flocs or fine particles. As will be appreciated, this premature latex inversion may undesirably viscosify the cement composition, resulting in a cement composition that is non-functional for use in subterranean cementing operations. Moreover, because of the premature inversion, the latex generally will not have the desired functionality in the cement composition.